Optical film, polarizing plate including the optical film, and liquid crystal display apparatus including the polarizing plate

ABSTRACT

An optical film includes: a protective layer; and a contrast ratio improvement layer including a first resin layer and a second resin layer facing the first resin layer, the second resin layer and the first resin layer being sequentially stacked from a lower surface of the protective layer, wherein the second resin layer has a refractive index greater than that of the first resin layer. The first resin layer has a patterned portion with at least two embossed optical patterns and flat sections immediately adjacent to and between the embossed optical patterns. The patterned section is in at least a portion thereof facing the second resin layer. A polarizing plate including the optical film and a liquid crystal display apparatus including the polarizing plate are also provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.16/155,755, filed on Oct. 9, 2018, which claims priority to and thebenefit of Korean Patent Application No. 10-2017-0144980, filed on Nov.1, 2017 and Korean Patent Application No. 10-2018-0089938, filed on Aug.1, 2018, the entire contents of all of which are incorporated herein byreference.

BACKGROUND 1. Field

One or more aspects of example embodiments of the present disclosure arerelated to an optical film, a polarizing plate including the opticalfilm, and a liquid crystal display apparatus including the polarizingplate.

2. Description of the Related Art

A liquid crystal display (LCD) apparatus is operated in such a mannerthat light from a backlight unit is emitted (transmitted) through aliquid crystal panel. The light from the backlight unit isperpendicularly (normally) incident to a screen of the liquid crystaldisplay apparatus. As a result, a contrast ratio (CR) on a side surfaceof the liquid crystal display apparatus (e.g., the side contrast ratio)is lower than that on a front surface of the liquid crystal displayapparatus (e.g., the front contrast ratio). Therefore, development of anoptical film for improving a contrast ratio, including the side contrastratio, is being conducted.

An optical film includes an optical pattern, a high refractive indexlayer, and a low refractive index layer to improve a side contrastratio. The side contrast ratio may be improved by the optical pattern,which includes a flat section and an embossed optical pattern that arealternatively formed. However, although the contrast ratio on the sidesurface is somewhat improved by the optical film, when light emitted tothe front surface is disturbed by the optical pattern, the frontcontrast ratio is reduced. Further, external light is incident on theoptical pattern even when an optical display device is not driven,resulting in an increase in reflectance.

SUMMARY

One or more aspects of example embodiments of the present disclosure aredirected toward an optical film that is capable of improving a contrastratio on a front surface (e.g., the front contrast ratio), increasing aviewing angle, and lowering reflectance.

One or more aspects of example embodiments of the present disclosure aredirected toward an optical film that is capable of lowering a degree ofa color shift on side surfaces.

One or more aspects of example embodiments of the present disclosure aredirected toward an optical film that has an excellent externalappearance when a composition for a high refractive index layer is wellcured, thereby minimizing or reducing separation of a dye from the highrefractive index layer.

One or more aspects of example embodiments of the present disclosure aredirected toward an optical film that has an excellent externalappearance when a composition for a low refractive index layer is wellcured, thereby minimizing or reducing separation of a dye from the lowrefractive index layer.

One or more aspects of example embodiments of the present disclosure aredirected toward an optical film that is capable of lowering lightleakage to the side surfaces, and improving a black mode contrast ratioby reducing the amount of light that is emitted to the side surfaces inblack mode.

One or more aspects of example embodiments of the present disclosure aredirected toward an optical film including a second resin layer toimprove brightness, and which has high light transmittance despiteincluding a dye.

One or more aspects of example embodiments of the present disclosure aredirected toward a polarizing plate and an optical display deviceincluding the optical film according to embodiments of the presentdisclosure.

According to one or more example embodiments of the present disclosure,an optical film includes a protective layer and a contrast ratioimprovement layer, the contrast ratio improvement layer including afirst resin layer and a second resin layer facing the first resin layer,the second resin layer and the first resin layer being sequentiallystacked from a lower surface of the protective layer, wherein the secondresin layer has a refractive index greater than that of the first resinlayer. The first resin layer has a patterned portion with at least twoembossed optical patterns and flat sections between and immediatelyadjacent to the embossed optical patterns, the patterned portion beingin at least a portion thereof facing the second resin layer. Acorresponding one of the embossed optical patterns has a base angle (θ)of about 75° to about 90°, and the patterned portion satisfiesExpression 1:1<P/W≤10,  Expression 1

wherein, in Expression 1,

P is a pitch (unit: μm) of the patterned portion, and

W is a maximum width (unit: μm) of the embossed optical pattern.

The first resin layer and/or the second resin layer includes a metalcomplex dye and/or an organic black dye.

According to one or more example embodiments of the present disclosure,a polarizing plate includes a polarizing film and the optical film, theoptical film being on the polarizing film.

According to one or more example embodiments of the present disclosure,a liquid crystal display apparatus includes the polarizing plate.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentdisclosure will become more apparent to those of ordinary skill in theart by describing example embodiments thereof in more detail withreference to the accompanying drawings, in which:

FIG. 1 is a cross-sectional view illustrating an optical film accordingto an example embodiment of the present disclosure;

FIG. 2 illustrates a first zone and a second zone of a second resinlayer in the optical film of the present disclosure;

FIG. 3 is a cross-sectional view illustrating a polarizing plateaccording to an example embodiment of the present disclosure;

FIG. 4 is a scanning electron microscope (SEM) image of a cross sectionof an optical film according to Comparative Example 4; and

FIG. 5 is a plot of transmittance (TT) versus wavelength for a series ofcolor dyes included in an organic black dye as used according to anexample embodiment of the present disclosure.

DETAILED DESCRIPTION

Example embodiments will be described in more detail with reference tothe accompanying drawings to provide a thorough understanding of thedisclosure to those skilled in the art. It should be understood that thepresent disclosure may be embodied in different ways, and is not limitedto the described embodiments. In the drawings, portions irrelevant tothe description may be omitted for clarity. Like components will bedenoted by like reference numerals throughout the specification, andduplicative descriptions thereof may not be provided.

In the drawings, the thicknesses of layers, films, panels, regions,etc., may be exaggerated for clarity. As used herein, spatially relativeterms such as “upper” and “lower” are defined with reference to theaccompanying drawings. Thus, it will be understood that “upper” can beused interchangeably with “lower”, and “lower” can be usedinterchangeably with “upper”. It will be understood that when a layer orelement is referred to as being “on” another layer or element, it can bedirectly formed on the other layer or element, or intervening layer(s)or element(s) may also be present. In contrast, when a layer or elementis referred to as being “directly on” another layer or element, nointervening layers or elements are present.

Expressions such as “at least one of”, “one of”, “selected from”, “atleast one selected from”, and “one selected from”, when preceding a listof elements, modify the entire list of elements and do not modify theindividual elements of the list. Further, the use of “may” whendescribing embodiments of the disclosure refers to “one or moreembodiments of the disclosure.”

As used herein, the terms “horizontal direction” and “verticaldirection” refer to a transverse direction and a longitudinal directionof a rectangular screen of a liquid crystal display, respectively. Asused herein, the term “side surface” refers to a region in which θranges from 0° to 30° or from 0° to 60° in the spherical coordinatesystem represented by (ϕ, θ). The term “front” refers to a regionindicated by (0°, 0°), a left end point is indicated by (180°, 90°), anda right end point is indicated by (0°, 90°) with reference to thehorizontal direction.

As used herein, the term “top part” refers to a portion located at anuppermost portion of an embossed optical pattern.

As used herein, the term “aspect ratio” refers to a ratio of maximumheight of an embossed optical pattern to a maximum width thereof(maximum height/maximum width).

As used herein, the term “pitch” refers to the distance between adjacentembossed optical patterns, for example, the sum of a maximum width ofone optical pattern and a width of one flat section immediately adjacentto the optical pattern.

As used herein, the term “in-plane retardation (Re)” is a value at awavelength of 550 nm and is represented by Expression A:Re=(nx−ny)×d.  Expression A

In Expression A, nx and ny are the refractive indexes at a wavelength of550 nm in a slow axis direction and a fast axis direction of acorresponding protective layer or base layer, respectively, and d is athickness of the corresponding protective layer or base layer (unit:nm).

As used herein, the term “(meth)acryl” refers to acryl and/or methacryl.

When a metal complex dye and/or an organic black dye is added to a firstresin layer and/or a second resin layer in an optical film, where theoptical film includes a patterned portion, a contrast ratio on the frontsurface (e.g., front contrast ratio) may be improved, reflectance may belowered, a viewing angle may be improved, and a degree of a color shifton the side surfaces may be lowered, without affecting an improvement incontrast ratio on the side surfaces (e.g., side contrast ratio) by thepatterned portion.

Hereinafter, an optical film according to an example embodiment of thepresent disclosure will be described with reference to FIG. 1. FIG. 1 isa cross-sectional view illustrating the optical film according to anexample embodiment of the present disclosure.

Referring to FIG. 1, in an optical film 10, a contrast ratio improvementlayer 200 is formed on a lower surface of a protective layer 100.

Protective Layer

The protective layer 100 may be formed on one surface of the contrastratio improvement layer 200 to support the contrast ratio improvementlayer 200. The protective layer 100 may be directly formed on a secondresin layer 220 of the contrast ratio improvement layer 200 to reduce athickness of the optical film 10. The expression “directly formed on”indicates that no intervening layers (such as an adhesive layer, abonding layer, or an adhesive bonding layer) are interposed between theprotective layer 100 and the contrast ratio improvement layer 200.

The contrast ratio improvement layer 200 may be formed on a lightincidence surface of the protective layer 100. Light passing through thecontrast ratio improvement layer 200 may be further emitted(transmitted) through the protective layer 100.

The protective layer 100 may have a total visible light transmittance ofabout 90% or more, for example, about 90% to about 100%. Within theseranges, the protective layer 100 may transmit incident light withoutaffecting (e.g., the intensity of) the incident light.

The protective layer 100 may be a protective film or a protectivecoating layer that has a light incidence surface and a light exitsurface opposite to the light incidence surface. For example, a degreeof support for the contrast ratio improvement layer 200 may be increasedby using the protective film as the protective layer 100.

When the protective layer 100 is the protective film, the protectivelayer 100 may include a single layer of an optically transparent resinfilm. However, in some embodiments, the protective layer 100 may includea plurality of stacked resin films. The protective film may be formed bymelting and extruding a resin. In some embodiments, an elongationprocess may be further added. The resin may include at least oneselected from a cellulose ester-based resin (including triacetylcellulose (TAC) and/or the like), a cyclic polyolefin-based resin(including amorphous cyclic polyolefin (COP)), a polycarbonate-basedresin, a polyester-based resin (including a polyethylene terephthalate(PET) and/or the like), a polyether sulfone-based resin, apolysulfone-based resin, a polyamide-based resin, a polyimide-basedresin, a non-cyclic-polyolefin-based resin, a polyacrylate-based resin(including a polymethylmethacrylate resin and/or the like), a polyvinylalcohol-based resin, a polyvinyl chloride-based resin, and apolyvinylidene chloride-based resin.

The protective film may be a non-elongated film. However, the protectivefilm may be a retardation film or an isotropic optical film, which mayexhibit retardation properties when the resin forming the film iselongated according to a particular method. In some embodiments, theprotective film may be an isotropic optical film having a Re of about 0nm to about 60 nm, for example, about 40 nm to about 60 nm. Within theseranges, a high image quality may be attained by compensating for aviewing angle. Herein, the term “isotropic optical film” refers to afilm in which nx, ny, and nz are substantially the same (wherein nzrepresents a refractive index in a direction orthogonal to therefractive indices nx and ny). Herein, the expression “substantially thesame” includes not only a case in which nx, ny, and nz are completelythe same, but also a case in which there is an acceptable or suitablemargin of error between nx, ny, and nz. In some embodiments, theprotective film may be a retardation film having a Re of about 60 nm ormore. For example, the protective film may have a Re of about 60 nm toabout 500 nm, for example, about 60 nm to about 300 nm. In someembodiments, the protective film may have a Re of about 8,000 nm ormore, for example about 10,000 nm or more, about 10,100 nm to about30,000 nm, or about 10,100 nm to about 15,000 nm. Within these ranges,it is possible to prevent or reduce a rainbow spot from being visibleand further improve light diffusion through the contrast ratioimprovement layer 200.

The protective coating layer may be made of an ultraviolet (UV) curableresin composition including a UV curable compound and an initiator. TheUV curable compound may include at least one selected from a cationpolymerizable curable compound, a radical polymerizable curablecompound, a urethane resin, and a silicone-based resin. The cationpolymerizable curable compound may include at least one selected from anepoxy-based compound having at least one epoxy group in a moleculethereof and an oxetane-based compound having at least one oxetane ringin a molecule thereof. The epoxy-based compound may include at least oneselected from a hydrogenated epoxy-based compound, a chain aliphaticepoxy-based compound, a cyclic aliphatic epoxy-based compound, and anaromatic epoxy-based compound.

The radical polymerizable curable compound may be obtained by reacting a(meth)acrylate monomer having at least one (meth)acryloyloxy group in amolecule thereof with two or more types or kinds of functionalgroup-containing compounds, and may include a (meth)acrylate oligomerhaving at least two (meth)acryloyloxy groups in a molecule thereof.Non-limiting examples of the (meth)acrylate monomer may include amonofunctional (meth)acrylate monomer having a single (meth)acryloyloxygroup in a molecule thereof, a bifunctional (meth)acrylate monomerhaving two (meth)acryloyloxy groups in a molecule thereof, and apolyfunctional (meth)acrylate monomer having three or more(meth)acryloyloxy groups in a molecule thereof. The (meth)acrylateoligomer may include at least one selected from a urethane(meth)acrylate oligomer, a polyester (meth)acrylate oligomer, an epoxy(meth)acrylate oligomer, and/or the like. The initiator may cure the UVcurable compound. The initiator may include a photo-cationic initiatorand/or a photosensitizer. Any suitable initiator available in the artmay be used as the photo-cationic initiator and the photosensitizer.

A thickness of the protective layer 100 may be about 5 μm to about 200μm, for example, about 30 μm to about 120 μm. When the protective layer100 is provided as a protective film, a thickness of the protective filmmay be about 30 μm to about 100 μm, for example, about 50 μm to about 90μm. When the protective layer 100 is provided as a protective coatinglayer, a thickness of the protective coating layer may be about 5 μm toabout 50 μm. Within these ranges, the protective layer 100 may be usedin a polarizing plate.

A surface treatment layer (such as a primer layer, a hard coating layer,a fingerprint-resistant layer, an anti-reflection layer, an anti-glarelayer, a low reflection layer, and/or an ultra-low reflection layer) maybe further formed on at least one surface (e.g., an upper surface and/ora lower surface) of the protective layer 100. The hard coating layer,the fingerprint-resistant layer, the anti-reflection layer, and/or thelike may provide an additional function to the protective layer 100, apolarizing film and/or the like. The primer layer may improve adhesionbetween the protective layer 100 and an adherend (for example, apolarizer).

Contrast Ratio Improvement Layer

The contrast ratio improvement layer 200 includes a first resin layer210 and a second resin layer 220 facing the first resin layer 210. Forexample, the contrast ratio improvement layer 200 may include the firstresin layer 210 and the second resin layer 220, where the first resinlayer 210 and the second resin layer 220 are in direct contact with eachother.

The first resin layer 210 is formed on a light incidence surface of thesecond resin layer 220. Light incident from a lower surface of the firstresin layer 210 may be emitted (e.g., transmitted) to the second resinlayer 220. The first resin layer 210 may diffuse light by refracting andemitting the light incident from the lower surface thereof in one ormore directions according to the incident position of the light.

The first resin layer 210 may be directly formed on the second resinlayer 220. A patterned portion is formed on an interface between thefirst resin layer 210 and the second resin layer 220 (e.g., where alower surface of the second resin layer 220 is in direct contact withthe first resin layer 210). FIG. 1 illustrates an embodiment in whichthe patterned portion is in complete contact with the second resin layer220. However, in some embodiments, the patterned portion is in contactwith at least or only a portion of the second resin layer 220. Anon-contacting portion between the second resin layer 220 and the firstresin layer 210 may be filled with air or a resin having a particularrefractive index. In some embodiments, the patterned portion may be incomplete contact with the second resin layer 220.

The patterned portion has at least two embossed optical patterns 221 anda flat section 222 between immediately adjacent embossed opticalpatterns 221. The patterned portion is configured so that a combinationof the embossed optical pattern 221 and the flat section 222 isrepeatedly formed.

The embossed optical pattern 221 may have a first surface 224 formed ata top portion thereof and at least one inclined surface 223 connected tothe first surface 224. The first resin layer 210 has an upper surface210 a and a lower surface 210 b. The upper surface 210 a of the firstresin layer 210 may be at an interface between the first resin layer 210and the second resin layer 220, and may correspond to (e.g., bepositioned in) the patterned portion.

The patterned portion may satisfy Expression 1, and the embossed opticalpattern 221 may have a base angle (θ) of about 75° to about 90°. Theterm “base angle (θ)” refers to an angle between the inclined surface223 of the embossed optical pattern 221 and a line corresponding to amaximum width W of the embossed optical pattern 221, the base anglebeing about 75° to about 90°. Here, the inclined surface 223 refers tothe inclined surface that is directly connected to the flat section 222of the embossed optical pattern 221. Within these ranges, it is possibleto improve a side contrast ratio and a contrast ratio at the same sidesurfaces viewing angle. For example, the base angle (θ) may be about75°, 76°, 77°, 78°, 79°, 80°, 81°, 82°, 83°, 84°, 85°, 86°, 87°, 88°,89°, or 90°, for example, about 80° to about 90°. P/W (a ratio of P toW) may be about 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.5,3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, or10, for example, about 1.2 to about 8.1<P/W≤10.  Expression 1

In Expression 1,

P is a pitch (unit: μm) of the patterned portion, and

W is the maximum width (unit: μm) of the embossed optical pattern.

FIG. 1 illustrates a case in which both base angles (θ) of the embossedoptical pattern are (simultaneously) the same. However, when the baseangle (θ) is about 75° to about 90°, an embossed optical pattern havingdifferent base angles (θ) may also be included in the scope of thepresent disclosure.

The embossed optical pattern 221 may be an optical pattern that has thefirst surface 224 formed at the top portion thereof and at least oneinclined surface 223 connected to the first surface 224. FIG. 1illustrates that the embossed optical pattern 221 is a trapezoidaloptical pattern in which two adjacent inclined surfaces 223 areconnected by the first surface 224, but embodiments of the presentdisclosure are not limited thereto. The embossed optical pattern 221 maybe an optical pattern having a rectangular cross section and/or a squarecross section, in addition to or instead of a trapezoidal cross section.In some embodiments, for example, the embossed optical pattern may havea trapezoidal, rectangular, and/or square cross-sectional shape.

Since the first surface 224 is formed at the top portion, light reachingthe second resin layer 220 may be further diffused by the first surface224 in an optical display device, thereby improving a viewing angle andbrightness. Therefore, an optical diffusion effect may be improved tominimize or reduce brightness loss. The first surface 224 may be a flatsurface and may also facilitate a manufacturing process of the opticalfilm 10. However, in some embodiments, the first surface 224 may have afine concave-convex surface or a curved surface. When the first surface224 is a curved surface, a lenticular lens pattern may be formed. FIG. 1illustrates a pattern in which a plane is formed at a top portion (firstsurface) thereof, an inclined surface thereof is a plane, and a crosssection thereof has a trapezoidal shape (for example, a prism patternhaving a truncated triangular cross-section, or a cut-prism shape).However, in some embodiments, an embossed optical pattern may have ashape in which a first surface is formed at a top portion and aninclined surface is a curved surface (for example, a contrast ratioimprovement layer having a cut-lenticular lens pattern such as atruncated lenticular lens pattern, or a cut-micro lens pattern such as atruncated micro-lens pattern). In some embodiments, a pattern may have across section in the form of an N-sided shape (such as a rectangularshape or a square shape), wherein N is an integer from 3 to 20.

The first surface 224 may be formed parallel to at least one selectedfrom the flat section 222, a bottom surface of the first resin layer210, and a top surface of the second resin layer 220 (e.g., an uppersurface of the second resin layer 220). FIG. 1 illustrates a case inwhich the first surface 224 of the embossed optical pattern 221, theflat section 222 thereof, the bottom surface of the first resin layer210, and the top surface of the second resin layer 220 are parallel toone another.

A width A of the first surface 224 may be about 0.5 μm to about 30 μm,for example, about 1 μm to about 15 μm. Within these ranges, theembossed optical pattern 221 may be used in an optical display device,and a contrast ratio improvement effect may be observed.

An aspect ratio (H1/W) of the embossed optical pattern 221 may be about0.1 to about 10, for example, about 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7,0.8, 0.9, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8,8.5, 9, 9.5, or 10, about 0.1 to about 7.0, about 0.1 to about 5.0, orabout 0.1 to about 1.0. Within these ranges, it is possible to improve acontrast ratio and a viewing angle at the side surfaces of an opticaldisplay device.

A maximum height H1 of the embossed optical pattern 221 may be greaterthan about 0 μm and equal to or less than about 20 μm, for example,greater than about 0 μm and equal to or less than about 15 μm, orgreater than about 0 μm and equal to or less than about 10 μm. Withinthese ranges, it is possible to improve a contrast ratio, a viewingangle, and brightness, and to prevent or reduce a Moiré phenomenon fromoccurring.

The maximum width W of the embossed optical pattern 221 may be greaterthan about 0 μm and equal to or less than about 20 μm, for example,greater than about 0 μm and equal to or less than about 15 μm, orgreater than about 0 μm and equal to or less than about 10 μm. Withinthese ranges, it is possible to improve a contrast ratio, a viewingangle, and brightness, and to prevent or reduce a Moiré phenomenon fromoccurring.

FIG. 1 illustrates the patterned portion in which embossed opticalpatterns are formed to have the same base angle, a first surface withthe same width, the same maximum height, and the same maximum width.However, adjacent embossed optical patterns may have different baseangles, first surfaces with different widths, different maximum heights,and different maximum widths.

The flat section 222 may emit (e.g., transmit) light passing through thefirst resin layer 210 to the second resin layer 220, thereby improvingbrightness at a front side of an optical display device.

A ratio (W/L) of the maximum width W of the embossed optical pattern 221to a width L of the flat section 222 may be greater than about 0 andequal to or less than about 9, for example, about 0.1, 0.2, 0.3, 0.4,0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9,2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, or 3.0, about 0.1 toabout 3, or about 0.15 to about 2. Within these ranges, it is possibleto reduce a difference between the front contrast ratio and the sidecontrast ratio, and to improve a contrast ratio at the same side viewingangle and at the same front viewing angle. In addition, a Moiréphenomenon may be prevented or reduced. The width L of the flat section222 may be about 1 μm to about 50 μm, for example, about 1 μm to about20 μm. Within these ranges, it is possible to improve brightness at afront side of an optical display device.

The maximum width W of one embossed optical pattern 221 and the flatsection 222 immediately adjacent to the embossed optical pattern 221form one pitch P. The pitch P may be about 1 μm to about 50 μm, forexample, about 1 μm to about 40 μm. Within these ranges, it is possibleto improve a contrast ratio and to prevent or reduce a Moiré phenomenon.

FIG. 1 illustrates an embodiment in which adjacent patterned portionshave the same pitch and the same maximum width. However, in someembodiments, adjacent patterned portions may have different pitches anddifferent maximum widths.

A refractive index of the first resin layer 210 may be greater thanabout 0 and less than about 1.52, for example, greater than or equal toabout 1.35 and less than about 1.50. Within these ranges, it is possibleto improve a light diffusion effect, facilitate manufacturing of anoptical display device, and significantly improve polarized lightdiffusion and a contrast ratio.

The first resin layer 210 may be made of a composition for a first resinlayer, which includes a curable resin. The composition for the firstresin layer may further include an initiator. The curable resin and theinitiator may be the same as those used in a composition for a secondresin layer. The composition for the first resin layer may furtherinclude an additive of the composition as used in the second resinlayer.

In some embodiments, the first resin layer 210 may be a non-adhesivelayer having no adhesion. When the first resin layer 210 is anon-adhesive layer, the optical film 10 may be stacked on an adherend(for example, a polarizing film) through an adhesive, a bonding agent,and/or an adhesive bonding agent.

In some embodiments, the first resin layer 210 may have an adhesiveproperty (e.g., be adhesive, or be an adhesive layer). When the firstresin layer 210 has the adhesive property, the optical film 10 may bestacked on an adherend without an additional adhesive, bonding agent, oradhesive bonding agent, thereby reducing a thickness of the optical film10.

In some embodiments, the first resin layer 210 may not include a metalcomplex dye and/or an organic black dye.

FIG. 1 illustrates that the embossed optical pattern 221 is formed toelongate in a stripe shape in a lengthwise direction. However, in someembodiments, the embossed optical pattern 221 may be formed in a dotshape. The term “dot” refers to that the embossed optical patterns 221are spaced apart from each other and are dispersed. In some embodiments,for example, the embossed optical pattern 221 may be formed to elongatein the stripe shape such that a viewing angle from a left or a right iswidened.

The second resin layer 220 has a refractive index greater than that ofthe first resin layer 210. Therefore, the contrast ratio improvementlayer 200 may improve a side contrast ratio by diffusing and emittinglight incident from a light incidence surface of the first resin layer210. Although the contrast ratio on the side surfaces is improved, it ispossible to minimize or reduce a reduction in a contrast ratio on thefront surface, reduce a difference between the contrast ratio on thefront surface and the contrast ratio on the side surfaces, and improve acontrast ratio at the same side viewing angle and at the same frontviewing angle. A refractive index difference between the second resinlayer 220 and the first resin layer 210 may be greater than or equal toabout 0.05, for example, about 0.05, 0.1, 0.15, 0.2, 0.25, or 0.3, forexample, about 0.05 to about 0.3, and more for example, about 0.05 toabout 0.2. Within these ranges, it is possible to significantly improveconcentrated light diffusion and a contrast ratio.

The refractive index of the second resin layer 220 may be greater thanor equal to about 1.50, for example, about 1.50, 1.55, 1.60, 1.65, or1.70, or about 1.55 to about 1.70. Within these ranges, it is possibleto improve a light diffusion effect.

The second resin layer 220 may include a metal complex dye and/or anorganic black dye, and a composition for a second resin layer mayinclude a curable resin.

After the metal complex dye and/or the organic black dye is dispersed(e.g., in the second resin layer 220), an average particle diameter(D50) thereof may be greater than about 0 nm and equal to or less thanabout 100 nm, for example, about 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80nm, 85 nm, 90 nm, 95 nm, or 100 nm, about 1 nm to about 100 nm, or about5 nm to about 80 nm. Within these ranges, it is possible to obtain theeffects of the present disclosure.

The average particle diameter of the metal complex dye and the organicand/or black dye may be significantly smaller than each of the maximumwidth W of the embossed optical pattern 221 and the width L of the flatsection 222. For example, a ratio of the average particle diameter ofthe metal complex dye and/or the organic black dye to the maximum widthW of the embossed optical pattern 221, the width L of the flat section222, and/or the width A of the first surface 224 of the embossed opticalpattern 221 (e.g., the average particle diameter of the metal complexdye and/or organic black dye: the maximum width W of the embossedoptical pattern 221, the width L of the flat section 222, and/or thewidth A of the first surface 224 of the embossed optical pattern 221)may be about 1:500 to about 1:800, for example, about 1:600 to about1:800. Within these ranges, it is possible to obtain the effects of thepresent disclosure.

The second resin layer 220 may include the metal complex dye and/or theorganic black dye having the above average particle diameter, therebyimproving the front contrast ratio, lowering the reflectance, andlowering the degree of a color shift on the side surfaces. Within theseaverage particle diameter ranges, when the metal complex dye and/or theorganic black dye is between adjacent embossed optical patterns 221,emission (or transmission) of light from the flat section 222 of thefirst resin layer 220 is not affected, thereby improving a frontcontrast ratio, and light emitted to a side surface of a pattern is notaffected, thereby also improving the side contrast ratio due to thepatterned portion. The second resin layer 220 may include the metalcomplex dye and/or the organic black dye, thereby improving a sidecontrast ratio and lowering the reflectance despite a layer increase. Itis possible to increase low black visibility caused by side lightleakage of an LCD panel. Panel reflectance measured at the protectivelayer 100 with respect to the optical film 10 may be less than about 5%,for example, about 0% to about 4.95%, or about 0% to about 4.9%. Withinthese ranges, reflectance may be lowered to improve an externalappearance.

In some embodiments, the metal complex dye and/or the organic black dyemay be included in an amount of about 0.01 wt % to about 10 wt %, forexample, in an amount of about 0.01 wt %, 1 wt %, 2 wt %, 3 wt %, 4 wt%, 5 wt %, 6 wt %, 7 wt %, 8 wt %, 9 wt %, or 10 wt %, in an amount ofabout 0.01 wt % to about 5.0 wt %, about 0.01 wt % to about 3.0 wt %, orabout 0.01 wt % to about 2.0 wt %, in an amount of about 0.01 wt % toabout 1.0 wt %, or in an amount of about 0.01 wt % to about 0.5 wt %with respect to a total weight of the second resin layer 220. Withinthese ranges, it is possible to improve the front contrast ratio, lowerthe reflectance, increase black visibility, and add the metal complexdye and/or the organic black dye to the second resin layer 220. Inaddition, it is possible to obtain an excellent dye dispersion andprevent or decrease a reduction in light transmittance of the secondresin layer 220.

The light transmittance of the second resin layer 220 may be about 50%to about 92%, for example, about 75% to about 85% at a wavelength of 550nm. Within these ranges, it is possible to (e.g., simultaneously)improve both the side contrast ratio due to a pattern and a frontcontrast ratio.

In some embodiments, the metal complex dye and/or the organic black dyemay be included in an entirety of (e.g., throughout) the second resinlayer 220. For example, when a space between immediately adjacentembossed optical patterns 220 (e.g., a corresponding one of the embossedoptical patterns and an immediately adjacent embossed optical pattern)is defined as a “first zone” and a space between a virtual surfaceconnecting the first surfaces 224 of the spaced apart embossed opticalpatterns 220 and the lower surface of the protective layer 100 isdefined as a “second zone” in the second resin layer 220, the secondresin layer 220 may include the first zone and the second zone, thefirst zone and the second zone may be in contact with each other, andthe metal complex dye and/or the organic black dye may be (e.g.,simultaneously) included in both of the first zone and the second zone.As such, the second resin layer 220 may be easily manufactured. FIG. 2illustrates a first zone 220 a and a second zone 220 b of the secondresin layer 220 in the described-above optical film 10. However, in someembodiments, the metal complex dye and/or the organic black dye may beincluded in the first zone and not included in the second zone.

Hereinafter, a metal complex dye will be described in more detail.

The metal complex dye may include a metal-containing black dye.

The metal complex dye may include a 1:1 metal complex dye and/or a 1:2metal complex dye. The term “1:1 metal complex dye” refers to a dye inwhich one metal atom is combined with one dye molecule. The term “1:2metal complex dye” refers to a dye in which one metal atom is combinedwith two dye molecules.

The metal may be or include chromium (Cr), nickel (Ni), cobalt (Co), orcopper (Cu), but embodiments of the present disclosure are not limitedthereto.

The dye molecule may include an azo-based molecule (for example, amonoazo-based molecule) including at least one selected from a hydroxylgroup, a carboxyl group, and an amino group. Therefore, it is possibleto further improve a side contrast ratio due to an optical pattern aswell as a front contrast ratio due to the metal complex dye, and alsofurther lower the reflectance and further increase black visibility.

In some embodiments, the metal complex dye may be a metal-containingazo-based dye and may have a C₆-C₂₀ monocyclic or multicyclic aromaticfunctional group. For example, the metal complex dye may include aC₈-C₁₅ monocyclic or multicyclic aromatic functional group (such as aphenyl group and/or a naphthalene group) as a monocyclic or multicyclicaromatic functional group. As a result, when the metal complex dye ismixed with a UV curable resin forming the second resin layer 220, the UVcurable resin may be well cured, thereby increasing hardness of thesecond resin layer 220 and preventing or reducing separation of themetal complex dye from the second resin layer 220.

In some embodiments, the metal complex dye may include a type or kind ofa dye, such as a red metal complex dye, a green metal complex dye,and/or a blue metal complex dye.

In some embodiments, the metal complex dye may include a mixture of ared metal complex dye, a green metal complex dye, and a blue metalcomplex dye.

A refractive index of the metal complex dye may be about 1.6 to about2.2, for example, about 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, or 2.2, or about1.9 to about 2.1. Within these ranges, when the metal complex dye isincluded in the second resin layer 220, a refractive index of the secondresin layer 220 may not be lowered.

The metal complex dye is not particularly limited, but commercially soldproducts may be used as the metal complex dye. For example, at least oneselected from Orasol® Black X55 (BASF Company, Ludwigshafen, Germany)and Orasol® Black X51 (BASF Company) may be used as the metal complexdye.

Hereinafter, an organic black dye will be described in more detail.

The organic black dye may be a nonmetallic-based dye not including ametal, and may include a black dye including only organic molecules.

The organic black dye has high dispersibility (minimum dispersion unitof 1 nm to 5 nm), high transparency, and high brightness. In contrast,an inorganic black dye including carbon black and/or the like has poordispersibility (minimum dispersion unit of 50 nm to 400 nm) and isopaque. Since the dispersion size of several nm in the organic black dyeis suitable for a micro pattern size and a solvent-free imprintingprocess, and because of its high dispersibility, reduction inbrightness, and high transmittance, the organic black dye may beselected instead of an inorganic black dye (e.g., carbon black).

A refractive index of the organic black dye may be about 1.6 to about2.2, for example, about 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, or 2.2, or about1.9 to about 2.1. Within these ranges, when the organic black dye isincluded in the second resin layer 220, a refractive index of the secondresin layer 220 may not be lowered.

In some embodiments, the organic black dye may be a trichromatic dyemixture. For example, the trichromatic dye mixture may be a mixture of afirst dye (orange color dye), a second dye (red color dye), and a thirddye (blue color dye). The first dye, the second dye, and the third dyemay have different maximum absorption wavelengths. The “maximumabsorption wavelength” is measured at a concentration of 5 mg/L (5 wt %)of each of the first to third dyes in a solvent, such as methyl ethylketone. The concentration range may be any concentration appropriate orsuitable for measuring transmittance.

The first dye may include a dye having a maximum absorption wavelengthof about 430 nm to about 450 nm, for example, about 440 nm. Theabsorption wavelength range may be about 360 nm to about 640 nm.

The second dye may include a dye having a maximum absorption wavelengthof about 510 nm to about 530 nm, for example, about 520 nm. Theabsorption wavelength range may be about 360 nm to about 740 nm.

The third dye may include a dye having a maximum absorption wavelengthof about 590 nm to about 610 nm, for example, about 600 nm. Theabsorption wavelength range may be about 360 nm to about 740 nm.

In some embodiments, the organic black dye may be a mixture in which thefirst dye is included in an amount of about 30 wt % to about 50 wt %,for example, about 30 wt %, 35 wt %, 40 wt %, 45 wt %, or 50 wt %, or inan amount of about 40 wt % to about 50 wt % with respect to the totalweight of the organic black dye. The second dye is included in an amountof about 1 wt % to about 20 wt %, for example, in an amount of about 1wt %, 2 wt %, 3 wt %, 4 wt %, 5 wt %, 6 wt %, 7 wt %, 8 wt %, 9 wt %, 10wt %, 11 wt %, 12 wt %, 13 wt %, 14 wt %, 15 wt %, 16 wt %, 17 wt %, 18wt %, 19 wt %, or 20 wt %, or in an amount of about 1 wt % to about 10wt % with respect to the total weight of the organic black dye. Thethird dye is included in an amount of about 30 wt % to about 50 wt %,for example, in an amount of about 30 wt %, 35 wt %, 40 wt %, 45 wt %,or 50 wt %, or in an amount of about 40 wt % to about 50 wt % withrespect to the total weight of the organic black dye. Within theseranges, it is possible to obtain a black dye having high brightness.

The first dye (orange color dye) may be or include an azo-based dye, forexample, an aromatic azo-based dye. For example, a dye represented byFormula 1 (for example, Synolon yellow Brown K-2RS, Kyung in SyntheticCorporation, Incheon, Korea) may be used as the first dye, butembodiments of the present disclosure are not limited thereto:

The second dye (red color dye) may include an azo-based dye, forexample, an aromatic azo-based dye. For example, a dye represented byFormula 2 (for example, Synolon rubine K-GFL, Kyung in SyntheticCorporation) may be used as the second dye, but embodiments of thepresent disclosure are not limited thereto:

The third dye (blue color dye) may include an azo-based dye, forexample, an aromatic azo-based dye. For example, a dye represented byFormula 3 (for example, Synolon navy blue K-GLS, Kyung in SyntheticCorporation) may be used as the third dye, but embodiments of thepresent disclosure is not limited thereto:

The organic black dye is not particularly limited, and commercially soldproducts may be used as the organic black dye. For example, BS01 (Kyungin Synthetic Corporation), BS02 (Kyung in Synthetic Corporation), and/orthe like may be used as the organic black dye.

A curable resin may include a UV curable resin and/or a thermosettingresin. The UV curable resin may be used to form the second resin layer220 in a short time, and so that a pattern shape is good or excellentwhen a pattern is formed. The curable resin may include a(meth)acrylic-based monomer, an oligomer, and/or a resin. As a resinhaving a high refractive index, the curable resin may include a resinhaving a repeating unit derived from a compound having a benzene ringstructure as a main skeleton.

After the curable resin is cured, the refractive index thereof may begreater than or equal to about 1.55, for example, about 1.58 to about1.62. Within these ranges, it is possible to secure the refractive indexof the second resin layer 220.

The composition for the second resin layer may further include aninitiator. The initiator may be for curing a curable resin, and mayinclude a photo initiator and/or a thermal initiator. Any suitableinitiator available in the art may be used as the photo initiator and/orthe thermal initiator. The photoinitiator may include one selected froma phosphorus, triazine, acetophenone, benzophenone, thioxanthone,benzoin, oxime, phenyl ketone initiators, and mixtures thereof. Theinitiator may be included in an amount of about 0.01 wt % to about 5 wt%, for example, in an amount of greater than about 0.5 wt % and equal toor less than about 5 wt %, or in an amount of about 2 wt % to about 5 wt% based on a solid content of the second resin layer 220 or thecomposition for the second resin layer. Within these ranges, thecomposition for the second resin layer may be sufficiently cured, andthe remaining amount of the initiator may prevent or reduce lighttransmission of the contrast ratio improvement layer 200 from beinglowered.

To ensure composition coatability, the composition for the second resinlayer may include solvents such as ethanol (EtOH), propylene glycolmonomethyl ether acetate (PGME), methyl ethyl ketone (MEK), and methylisobutyl ketone (MIBK), but embodiments of the present disclosure arenot limited thereto.

The composition for the second resin layer may further include anysuitable additive available in the art. The additive may include atleast one selected from a leveling agent, a surface controlling agent,an antioxidant, a defoamer, an ultraviolet absorbent, and aphotostabilizer.

A maximum thickness of the second resin layer 220 may be greater thanabout 0 μm and equal to or less than about 30 μm, for example, greaterthan about 0 μm and equal to or less than about 20 μm. Within theseranges, it is possible to prevent or reduce warpage (such as curling).

A difference (also called “wall thickness”) between a maximum thicknessof the second resin layer 220 and a maximum height of the embossedoptical pattern 221 may be greater than about 0 μm and equal to or lessthan about 30 μm, for example, greater than about 0 μm and equal to orless than about 20 μm, or greater than about 0 μm and equal to or lessthan about 10 μm. Within these ranges, it is possible to minimize ordecrease a reduction in the side contrast ratio.

In some embodiments, the second resin layer 220 may not include carbonblack.

In some embodiments, the first resin layer 210 may not include carbonblack.

A thickness of the contrast ratio improvement layer 200 may be about 10μm to about 100 μm, for example, about 10 μm to about 50 μm, or about 10μm to about 40 μm. Within these ranges, the contrast ratio improvementlayer 200 may be used in an optical display device.

The contrast ratio improvement layer 200 may be prepared using anysuitable method available in the art. For example, the contrast ratioimprovement layer 200 may be formed by coating the protective layer 100with the composition for the second resin layer, applying and curing theembossed optical pattern 221 and the flat section 222 to form the secondresin layer 220, and applying and curing the composition for the firstresin layer, but embodiments of the present disclosure are not limitedthereto.

Hereinafter, an optical film according to another example embodiment ofthe present disclosure will be described.

The optical film according to the present example embodiment is the sameas the optical film 10 according to the example embodiment of thepresent disclosure, except that a second resin layer does not includethe metal complex dye or the organic black dye, and a first resin layerincludes the metal complex dye and/or the organic black dye.

The metal complex dye and/or the organic black dye may be included in anamount of about 0.01 wt % to about 10 wt %, for example, in an amount ofabout 0.01 wt %, 1 wt %, 2 wt %, 3 wt %, 4 wt %, 5 wt %, 6 wt %, 7 wt %,8 wt %, 9 wt %, or 10 wt %, in an amount of about 0.01 wt % to about 5.0wt %, 0.01 wt % to 3.0 wt %, or 0.01 wt % to 2.0 wt %, or in an amountof about 0.01 wt % to about 1.0 wt % with respect to a total weight ofthe first resin layer. Within these ranges, it is possible to improve afront contrast ratio, increase black visibility, lower the reflectance,obtain high transmittance, and/or obtain excellent diffusion effect of ametal composite. The metal complex dye and the organic black dye may bethe same as described above.

In some embodiments, the second resin layer may not include carbonblack.

In some embodiments, the first resin layer may not include carbon black.

Hereinafter, an optical film for improving a contrast ratio according toanother example embodiment of the present disclosure will be described.

In the optical film according to the present example embodiment, asecond resin layer may include the metal complex dye and/or the organicblack dye. The metal complex dye and/or the organic black dye may beincluded only in a first zone of the second resin layer but not includedin second zone of the second resin layer. When the metal complex dyeand/or the organic black dye is included in a specific zone (e.g., thefirst zone), it is possible to further improve a contrast ratio andbrightness and prevent or decrease a reduction in light transmittance ofthe second resin layer.

The metal complex dye and/or the organic black dye may be included in anamount of about 0.01 wt % to about 10 wt %, for example, in an amount ofabout 0.01 wt %, 1 wt %, 2 wt %, 3 wt %, 4 wt %, 5 wt %, 6 wt %, 7 wt %,8 wt %, 9 wt %, or 10 wt %, in an amount of about 0.1 wt % to about 5.0wt %, about 0.01 wt % to about 3.0 wt %, or about 0.01 wt % to about 5wt %, or in an amount of about 0.01 wt % to about 1.0 wt % with respectto a total weight of the second resin layer. Within these ranges, it ispossible to improve the front contrast ratio, increase black visibility,lower the reflectance, obtain high transmittance, obtain excellentdiffusion effect of a metal composite, and remove a refractive indexdifference between the first zone and the second zone. The metal complexdye and the organic black dye may each be the same as described above.

In some embodiments, an absolute value of the refractive indexdifference between the first zone and the second zone may be about 0.02to about 0.20, for example, about 0.08 to about 0.20. Within theseranges, the refractive index difference between the first zone and thesecond zone may be reduced to prevent or decrease a reduction in lighttransmittance in each of the second resin layer, the optical film, and apolarizing plate.

In some embodiments, the second resin layer may not include carbonblack.

In some embodiments, the first resin layer may not include carbon black.

A polarizing plate according to an example embodiment of the presentdisclosure will be described with reference to FIG. 3. FIG. 3 is across-sectional view illustrating the polarizing plate according to anexample embodiment of the present disclosure.

Referring to FIG. 3, a polarizing plate 20 may include a polarizing film300 and an optical film. The optical film may be or include the opticalfilm 10 according to an example embodiment of the present disclosure.The optical film may be on a light exit surface of the polarizing film300. The optical film may diffuse polarized light passing through thepolarizing film 300, thereby improving a front contrast ratio, a sidecontrast ratio, and a viewing angle, and increasing black visibility.

The polarizing film 300 may polarize light incident from a liquidcrystal panel and transmit the polarized light to a contrast ratioimprovement layer 200. The polarizing film 300 is formed on a lightincidence surface of the contrast ratio improvement layer 200.

The polarizing film 300 may include a polarizer. For example, thepolarizer may include a polyvinyl alcohol-based polarizer uniaxiallyelongating a polyvinyl alcohol-based film, or a polyene-based polarizerdehydrating the polyvinyl alcohol-based film. A thickness of thepolarizer may be about 5 μm to about 40 μm. Within this range, thepolarizer may be used in an optical display device.

The polarizing film 300 may include the polarizer and a protective layerformed on at least one surface of the polarizer. The protective layermay protect the polarizer, thereby improving reliability of thepolarizing plate and increasing mechanical strength of the polarizingplate. The protective layer may include at least one selected from aprotective film and a protective coating layer, both being opticallytransparent. The protective layer may be the same as described above.

The polarizing plate may be formed using any suitable method. Forexample, the polarizing plate may be manufactured by preparing theoptical film through the above-described method and attaching thepolarizing film to another surface of the protective layer. Theattaching may be performed using any suitable water-based adhesiveand/or photocurable adhesive available in the art.

A liquid crystal display apparatus of the present disclosure may includethe polarizing plate of the present disclosure. In some embodiments, theliquid crystal display apparatus may include the polarizing plate as apolarizing plate at a visible side with respect to a liquid crystalpanel. The “polarizing plate at the visible side” may be positionedopposite to a screen, e.g., a light source, with respect to the liquidcrystal panel.

In some embodiments, the liquid crystal display apparatus may include abacklight unit, a first polarizing plate, a liquid crystal panel, and asecond polarizing plate, which are sequentially stacked. The secondpolarizing plate may include the polarizing plate of the presentdisclosure. The liquid crystal panel may use a vertical alignment (VA)mode, an in-plane switching (IPS) mode, a patterned vertical alignment(PVA) mode, or a super-patterned vertical alignment (S-PVA) mode, butembodiments of the present disclosure are not limited thereto. In someembodiments, the liquid crystal display apparatus may include thepolarizing plate as a polarizing plate at a light source side withrespect to the liquid crystal panel. The “polarizing plate at the lightsource side” is positioned at the light source side with respect to theliquid crystal panel. In some embodiments, both of the polarizing plateat the visible side and the polarizing plate at the light source sidewith respect to the liquid crystal panel may (e.g., simultaneously)include the polarizing plate of the present disclosure.

Hereinafter, the configuration and operation of the present disclosurewill be described in more detail with reference to example embodimentsof the present disclosure. However, it should be understood that theexample embodiments are provided for illustration only, and are not tobe in any way construed as limiting the present disclosure.

Example 1

0.15 parts by weight of a dye, i.e., Orasol® Black X55 (, and a powdered1:2 complex salt of Cr:an azo-based compound having an average particlediameter (D50) of 10 nm, BASF Company) was mixed into 100 parts byweight of a UV curable resin, i.e., SSC5760 (SHIN-A T&C, Seoul, Korea),and the resultant mixture was stirred at 2,000 rpm for 2 hours using adisperser to prepare a composition for a second resin layer.

100 parts by weight of an acrylic-based copolymer (i.e., adhesivePL8540) was mixed with 80 parts by weight of a diluting solvent (i.e.,methyl ethyl ketone), and the resultant mixture was stirred at 500 rpmfor 30 minutes using a stirrer to prepare a composition for a firstresin layer.

The composition for the second resin layer was applied on one surface(light incidence surface) of a protective layer (i.e., a polyethyleneterephthalate (PET) film (TA044, Toyobo Company, Osaka, Japan, athickness of 80 μm)) to prepare a coating layer. An embossed opticalpattern and a flat section were applied on the coating layer using afilm in which the embossed optical pattern and the flat section werealternately formed and were UV-cured with a light amount of 500 mJ/cm²to form a second resin layer.

The prepared composition for the first resin layer was coated on onesurface of the prepared second resin layer and was dried in an oven at atemperature of 90° C. for 4 minutes to form a first resin layer, therebymanufacturing an optical film for improving a contrast ratio. The firstresin layer is adhesive and has a refractive index lower than that ofthe second resin layer. A dye is included in an entirety of the secondresin layer ((e.g., simultaneously) in both of a first zone and a secondzone) in the optical film.

Table 1 shows a specification of a patterned portion of a contrast ratioimprovement layer.

One surface of the first resin layer of the optical film was laminatedon a PET film surface of a polarizing film (AMN-6143CPS (CO) having athree-layered structure of PET/PVA/COP, Samsung SDI, Yong-in, Korea) tomanufacture a polarizing plate.

Example 2

An optical film and a polarizing plate were manufactured insubstantially the same manner as in Example 1, except that 0.3 parts byweight of Orasol® Black X55 was used in forming a composition for asecond resin layer. The dye is included in an entirety of the secondresin layer ((e.g., simultaneously) in both of a first zone and a secondzone) in the optical film.

Example 3

An optical film and a polarizing plate were manufactured insubstantially the same manner as in Example 1, except that 100 parts byweight of a resin, i.e., ECOKOT-H903 (NC Chem, Suwon, Korea) was used inplace of the SSC5760, and 0.15 parts by weight of Orasol® Black X51 (apowdered 1:2 complex salt Cr:an azo-based compound having an averageparticle diameter (D50) of 10 nm, BASF Company) was used in place ofOrasol® Black X55 in forming a composition for a second resin layer. Thedye is included in an entirety of the second resin layer ((e.g.,simultaneously) in both of a first zone and a second zone) in theoptical film.

Example 4

An optical film and a polarizing plate were manufactured substantiallyin the same manner as in Example 1, except that 0.3 parts by weight ofOrasol® Black X51 as a black dye was used in place of Orasol® Black X55in forming a composition for a second resin layer. The dye is includedin an entirety of the second resin layer ((e.g., simultaneously) in bothof a first zone and a second zone) in the optical film.

Example 5

An optical film and a polarizing plate were manufactured insubstantially the same manner as in Example 1, except that 0.15 parts byweight of an organic black dye (an average particle diameter of 10 nm)was used in place of Orasol® Black X55 in forming a composition for asecond resin layer. The organic black dye, which is a trichromatic dyemixture, was prepared by mixing 45 wt % of an orange color dye, i.e.,Synolon yellow Brown K-2RS (Kyung in Synthetic Corporation), 10 wt % ofa red color dye, i.e., Synolon rubine K-GFL (Kyung in SyntheticCorporation), and a blue color dye, i.e., 45 wt % of Synolon navy blueK-GLS (Kyung in Synthetic Corporation). FIG. 5 is a plot oftransmittance versus wavelength for each color dye. The dye is includedin an entirety of the second resin layer ((e.g., simultaneously) in bothof a first zone and a second zone) in the optical film.

Example 6

A UV curable resin, i.e., SSC5760 (SHIN-A T&C) was used as a compositionfor a second resin layer.

100 parts by weight of an acrylic-based copolymer, i.e., adhesive resinPL8540 was mixed with 0.038 parts by weight of Orasol® Black X55 (havingan average particle diameter of 10 nm, BASF Company) and 80 parts byweight of a diluting solvent, (i.e., methyl ethyl ketone), and theresultant mixture was stirred at 500 rpm for 30 minutes using a stirrerto prepare a composition for a first resin layer.

The prepared composition for the second resin layer was applied on onesurface (light incidence surface) of a protective layer, i.e., a PETfilm (TA044 Toyobo Company, a thickness of 80 μm) to prepare a coatinglayer. An embossed optical pattern and a flat section were applied onthe coating layer using a film in which the embossed optical pattern andthe flat section were alternately formed, and were UV-cured with a lightamount of 500 mJ/cm² to form a second resin layer.

The prepared composition for the first resin layer was coated on onesurface of the prepared second resin layer and was dried in an oven at atemperature of 90° C. for 4 minutes to form a first resin layer, therebymanufacturing an optical film. The first resin layer is adhesive and hasa refractive index lower than that of the second resin layer.

A polarizing plate was manufactured using the optical film insubstantially the same manner as in Example 1.

Example 7

An optical film and a polarizing plate were manufactured insubstantially the same manner as in Example 6, except that 0.076 partsby weight of Orasol® Black X55 was used in forming a composition for afirst resin layer.

Example 8

100 parts by weight of an acrylic-based copolymer, i.e., adhesive resinPL8540, was mixed with 80 parts by weight of a diluting solvent, i.e.,methyl ethyl ketone, and the resultant mixture was stirred at 500 rpmfor 30 minutes using a stirrer to prepare a composition for a firstresin layer.

100 parts by weight of a UV curable resin, i.e., SSC5760 (SHIN-A T&C)was used as a composition for a second zone of a second resin layer.

A certain amount of a dye, i.e., Orasol® Black X55 (a powdered 1:2complex salt of Cr:an azo-based compound having an average particlediameter (D50) of 10 nm, BASF Company) was mixed into 100 parts byweight of a UV curable resin, i.e., SSC5760 (SHIN-A T&C), and theresultant mixture was stirred at 2,000 rpm for 2 hours using a disperserto prepare a composition for a first zone of the second resin layer.

The composition for the first resin layer was applied on a PET filmsurface (light exit surface) of a polarizing film (product name:AMN-6143CPS (CO) having a three-layered structure of PET/PVA/COP,Samsung SDI) to prepare a coating layer. An embossed optical pattern anda flat section were applied on the coating layer using a film in whichthe embossed optical pattern and the flat section were alternatelyformed, and were UV-cured with a light amount of 500 mJ/cm² to form afirst resin layer.

The prepared composition for the first zone of the second resin layerwas applied only between embossed optical patterns of the first resinlayer. The prepared composition for the second zone of the second resinlayer was applied on an applied layer. UV curing was performed with alight amount of 500 mJ/cm² to manufacture a polarizing plate.

Table 1 shows a specification of a patterned portion of a contrast ratioimprovement layer. A dye was included only in the first zone and not inthe second zone of the second resin layer. In forming the compositionfor the first zone of the second resin layer, Orasol® Black X55 wasadded to the second resin layer of the finally manufactured polarizingplate so as to have the contents shown in Table 2.

Example 9

A polarizing plate was manufactured in substantially the same manner asin EXAMPLE 8, except that Orasol® Black X55 was added to a second resinlayer so as to have the contents shown in Table 2.

Example 10

A polarizing plate was manufactured in substantially the same manner asin Example 8, except that Orasol® Black X51 was used instead of Orasol®Black X55 and was added to a second resin layer so as to have thecontents shown in Table 2.

Comparative Example 1

A polarizing plate (product name: AMN-6143CPS (CO) having a structure ofPET/PVA/COP, Samsung SDI) was used without an optical film for improvinga contrast ratio.

Comparative Example 2

An optical film for improving a contrast ratio and a polarizing platewere manufactured in substantially the same manner as in Example 1,except that Orasol® Black X55 was not included in a second resin layer.

Comparative Example 3

An optical film and a polarizing plate were manufactured insubstantially the same manner as in Example 1, except that 0.5 parts byweight of a light absorbent (xx-2740 Sekisui Company, Osaka, Japan,having an average diameter R (D50) of 6 μm) coated with a lightabsorption layer including carbon black with an acrylic-based lightdiffuser on a surface thereof was used in place of Orasol® Black X55 informing a composition for a second resin layer.

Comparative Example 4

An optical film and a polarizing plate were manufactured insubstantially the same manner as in Example 6, except that 0.5 parts byweight of a light absorbent (xx-2740 Sekisui Company, having an averagediameter R (D50) of 6 μm) coated with a light absorption layer includingcarbon black with an acrylic-based light diffuser on a surface thereofwas used in place of Orasol® Black X55 (used as a light absorbent) informing a composition for a second resin layer.

TABLE 1 Width A (μm) Maximum height H1 Maximum width of first surfaceBase angle (°) Optical pattern (μm) of embossed (μm) of embossed ofembossed of embossed Width L (μm) Pitch P shape optical pattern opticalpattern optical pattern optical pattern of flat section (μm) Cut-prism 58 6.7 86 7 15 (Trapezoidal, embossed pattern)

The physical properties of each of the polarizing plates and opticalfilms of the Examples and Comparative Examples were evaluated.Evaluation results are shown in Table 2, Table 3, and FIG. 4.

Panel reflectance: The optical films laminated on the polarizing film ofthe Examples and Comparative Examples were subsequently laminated on anSUHD 55-inch liquid crystal panel having an LCD VN type or kind SamsungElectronics using an adhesive having a refractive index of 1.46 to 1.50,and then, reflectance was measured in a wavelength range of 320 nm to800 nm in an SCI reflection mode (D65 light source) using a reflectancemeter, e.g., a spectrophotometer (CM-2600D Konica Minolta, Tokyo,Japan). A Y(D65) value was measured.

Manufacture of Polarizing Plate at Light Source Side

A polyvinyl alcohol film was elongated to three times its originallength at a temperature of 60° C., allowed to adsorb iodine, and thenelongated to 2.5 times the first elongated length in an aqueous boricacid solution having a temperature of 40° C. to thereby prepare apolarizer. A base layer, e.g., a triacetyl cellulose film (thickness of80 μm) was bonded to both surfaces of the polarizer (e.g.,simultaneously) using a polarizing plate adhesive (Z-200 Nippon GohseiCompany, Osaka, Japan) to manufacture a polarizing plate. Themanufactured polarizing plate was used as a polarizing plate at a lightsource side.

Manufacture of Module for Liquid Crystal Display Apparatus

The manufactured polarizing plate at the light source side, liquidcrystal panel (PVA mode) and each of the polarizing plates manufacturedin the Examples and Comparative Examples were sequentially assembled tomanufacture a module for a liquid crystal display apparatus. Aprotective layer was positioned at an outermost position of each of thepolarizing plates manufactured in the Examples and Comparative Examples.

A light-emitting diode (LED) light source, a light guide plate, and themodule for the liquid crystal display apparatus were assembled tomanufacture a liquid crystal display apparatus including an edge type orkind LED light source (having substantially the same configuration as aSamsung TV (55 inches, model name: UN55KS8000F) except for theconfiguration of the modules for liquid crystal display apparatus in theExamples and Comparative Examples.

Front brightness was measured in each of a white mode and a black modeon a front surface (0°, 0°) and a side surface (0°, 80°) of a sphericalcoordinate system using EZ CONTRAST X88RC (EZXL-176R-F422A4 ELDIMCompany, Hérouville-Saint-Clair, France).

A relative contrast ratio on the front surface was calculated as a ratioof a brightness of the white mode to a brightness value of the blackmode in the spherical coordinate system (0°, 0°). A contrast ratio onthe side surfaces was calculated as a ratio of a brightness of the whitemode to a brightness value of the black mode in the spherical coordinatesystem (0°, 80°).

Front relative brightness in a front white mode was calculated as aratio of brightness of a corresponding Example or Comparative Example tobrightness of Comparative Example 1 in the white mode. Front relativebrightness in the black mode was calculated as a ratio of brightness ofa corresponding Example or Comparative Example to brightness ofComparative Example 1 in the white mode.

A skin (side) color shift was evaluated by using EZCONTRAST X88RC(EZXL-176R-F422A4, ELDIM Company). A low degree of shift indicatesexcellent properties.

An external appearance of the optical film was evaluated as being goodor suitable when stripe patterns and unusual features were not visiblein the external appearance. The external appearance was evaluated asbeing defective or unsuitable when stripe patterns or convex surfaceswere generated.

Light transmittance of the polarizing plate was evaluated using V7100Jasco Company (Hachioji, Japan).

TABLE 2 Examples 1 2 3 4 5 6 7 8 9 10 First Refractive 1.481 1.481 1.4811.481 1.481 1.481 1.481 1.481 1.481 1.481 resin index layer X55 0 0 0 00 0.038 0.076 0 0 0 (low content refractive (wt %) index layer) SecondRefractive 1.572 1.572 1.585 1.572 1.572 1.572 1.572 1.572 1.572 1.572resin index layer X55 content 0.15 0.3 0 0 0 0 0 0.15 0.30 0 (high (wt%) refractive X51 content 0 0 0.15 0.3 0 0 0 0 0 0.15 index (wt %)layer) Organic black 0 0 0 0 0.15 0 0 0 0 0 dye (wt %) Dye First FirstFirst First First First First First First First position Zone + Zone +Zone + Zone + Zone + resin resin zone zone zone Second Second SecondSecond Second layer layer Zone Zone Zone Zone Zone Front White mode 9287 91 92 92 92 88 94 89 95 relative Black mode 124 118 123 123 125 126119 125 119 126 brightness (%) Contrast (0°, 0°) 74.2 73.7 74.0 74.873.6 73 73.9 75.2 74.8 75.4 ratio (0°, 80°) 141 142 141 141 141 141 142142 141 141 (%) Panel 4.82 4.62 4.81 4.83 4.60 4.80 4.59 4.91 4.81 4.92reflectance (%) Skin color Left and 0.010 0.010 0.010 0.011 0.010 0.0100.011 0.010 0.011 0.011 shift right (Δxy@45°) Up and 0.009 0.008 0.0090.009 0.009 0.008 0.009 0.009 0.008 0.008 down External appearance GoodGood Good Good Good Good Good Good Good Good Light transmittance (%)39.227 36.437 39.192 36.332 39.437 39.335 36.214 41.122 38.567 41.254

TABLE 3 Comparative Example 1 2 3 4 First resin Refractive — 1.481 1.4811.481 (low index refractive Carbon — 0 0 0.5 index layer) black (wt %)Second resin Refractive — 1.5729 1.572 1.572 (high index refractiveCarbon — 0 0.5 0 index layer) black content (wt %) Front relative White100 95 91 92 brightness mode (%) Black mode 100 136 130 132 Contrast(0°, 0°) 100 69.9 70.0 69.7 ratio (%) (0°, 80°) 100 140 141 140 Panelreflectance (%) 4.95 5.18 5.11 5.12 Skin color Left and 0.0161 0.0100.010 0.011 shift right (Δxy@45°) Up and 0.009 0.009 0.008 0.009 downExternal appearance Good Good Bad Bad (Convex (Convex phenomenonphenomenon and and generation of generation of striped striped pattern)pattern) Light transmittance (%) 43.877 43.237 39.231 39.512

As shown in Tables 2 and 3 (e.g., by the improved performance of theExamples in Table 2 compared to the Comparative Examples in Table 3),the optical film according to embodiments of the present disclosure mayimprove the front contrast ratio and the side contrast ratio, lower thereflectance, have increase light transmittance, and lower the degree ofthe skin (side) color shift. In particular, the optical film accordingto embodiments of the present disclosure may allow the front contrastratio to be greater than 70% and the reflectance to be less than 5%.Since each layer is well cured and dyes are well dissolved and mixed,the optical film may have a good external appearance.

Accordingly, embodiments of the present disclosure provide an opticalfilm that is capable of improving a front contrast ratio and loweringreflectance. The present disclosure provides an optical film that iscapable of lowering a degree of a side color shift and increasing aviewing angle. The present disclosure provides an optical film that hasan excellent external appearance because a composition for a highrefractive index layer is well cured and dyes are well dissolved andmixed in a high refractive index resin. The present disclosure providesan optical film that has an excellent external appearance because acomposition for a low refractive index layer is well cured and dyes arewell dissolved and mixed in a low refractive index resin. The presentdisclosure provides an optical film that is capable of lowering lightleakage to a side surface and improving a black mode contrast ratio byreducing light that is emitted to the side surface in black mode. Thepresent disclosure provides an optical film that includes a second resinlayer that improves brightness and has high light transmittance despiteincluding a dye. The present disclosure provides a polarizing plate andan optical display device, each including the optical film of thepresent disclosure, and being capable of improving a side contrastratio, lowering reflectance, and increasing black visibility.

In contrast, an external appearance of Comparative Example 3 andComparative Example 4 including carbon black is poor, a high degree of aside color shift thereof is high, and panel reflectance thereof is high,and thus, black visibility thereof is low. In addition, referring toFIG. 4 (which shows a cross-sectional scanning electron microscope (SEM)image of an optical film for improving a contrast ratio according toComparative Example 4), when the carbon black (spherical element in FIG.4) is included, the carbon black does not match the optical patternsize, and thus, the effects of the present disclosure cannot beobtained.

As used herein, the terms “use”, “using”, and “used” may be consideredsynonymous with the terms “utilize”, “utilizing”, and “utilized”,respectively.

As used herein, the terms “substantially”, “about”, and similar termsare used as terms of approximation and not as terms of degree, and areintended to account for the inherent deviations in measured orcalculated values that would be recognized by those of ordinary skill inthe art.

Also, any numerical range recited herein is intended to include allsubranges of the same numerical precision subsumed within the recitedrange. For example, a range of “1.0 to 10.0” is intended to include allsubranges between (and including) the recited minimum value of 1.0 andthe recited maximum value of 10.0, that is, having a minimum value equalto or greater than 1.0 and a maximum value equal to or less than 10.0,such as, for example, 2.4 to 7.6. Any maximum numerical limitationrecited herein is intended to include all lower numerical limitationssubsumed therein and any minimum numerical limitation recited in thisspecification is intended to include all higher numerical limitationssubsumed therein. Accordingly, Applicant reserves the right to amendthis specification, including the claims, to expressly recite anysub-range subsumed within the ranges expressly recited herein.

While one or more example embodiments have been described with referenceto the drawings, it will be understood by those of ordinary skill in theart that various changes in form and details may be made therein withoutdeparting from the spirit and scope of the present disclosure as definedby the following claims and equivalents thereof.

What is claimed is:
 1. An optical film comprising: a protective layer;and a contrast ratio improvement layer comprising a first resin layerand a second resin layer facing the first resin layer, the second resinlayer and the first resin layer being sequentially stacked from a lowersurface of the protective layer, wherein the second resin layer has arefractive index greater than that of the first resin layer, and whereinthe second resin layer has a light transmittance of about 50% to about92% at a wavelength of 550 nm, the first resin layer has a patternedportion with at least two embossed optical patterns and flat sectionsbetween and immediately adjacent to the embossed optical patterns, thepatterned portion being in at least some region of the first resin layerfacing the second resin layer and satisfying Expression 1, acorresponding one of the embossed optical patterns has a base angle (θ)of about 75° to about 90°, and the first resin layer comprises a metalcomplex dye and/or an organic black dye:1<P/W≤10,  Expression 1 wherein, in Expression 1, P is a pitch (unit:μm) of the patterned portion, and W is a maximum width (unit: μm) of thecorresponding one of the embossed optical patterns.
 2. The optical filmof claim 1, wherein the metal complex dye and/or the organic black dyeis comprised in an amount of about 0.01 wt % to about 10 wt % in thefirst resin layer.
 3. The optical film of claim 1, wherein the metalcomplex dye and/or the organic black dye has an average particlediameter (D50) of about 1 nm to about 100 nm.
 4. The optical film ofclaim 1, wherein the metal complex dye is a black dye containingchromium (Cr), nickel (Ni), cobalt (Co), or copper (Cu).
 5. The opticalfilm of claim 4, wherein the metal complex dye is a black dye containingchromium.
 6. The optical film of claim 1, wherein the metal complex dyeis a metal azo-based dye.
 7. The optical film of claim 1, wherein themetal complex dye is an azo-based dye having a C₆-C₂₀ monocyclic ormulticyclic aromatic functional group.
 8. The optical film of claim 1,wherein the metal complex dye is an azo-based dye containing chromiumand having a C₆-C₂₀ monocyclic or multicyclic aromatic functional group,has an average particle diameter (D50) of about 1 nm to about 100 nm,and is comprised in an amount of about 0.01 wt % to about 10 wt % withrespect to a total weight of the first resin layer.
 9. The optical filmof claim 1, wherein the organic black dye comprises a first dye having amaximum absorption wavelength of about 430 nm to about 450 nm, a seconddye having a maximum absorption wavelength of about 510 nm to about 530nm, and a third dye having a maximum absorption wavelength of about 590nm to about 610 nm.
 10. The optical film of claim 9, wherein each of thefirst dye, the second dye, and the third dye comprises an azo-based dye.11. The optical film of claim 10, wherein the first dye is representedby Formula 1, the second dye is represented by Formula 2, and the thirddye is represented by Formula 3:


12. The optical film of claim 1, wherein the first resin layer isadhesive.
 13. The optical film according to claim 1, wherein theembossed optical pattern has a trapezoidal, a rectangular, orsquare-shaped cross-sectional shape.
 14. A polarizing plate comprising:a polarizing film; and the optical film of claim 1, the optical filmbeing on a light exit surface of the polarizing film.
 15. A liquidcrystal display apparatus comprising the polarizing plate of claim 14.